rrdtool plugin: Respect RandomTimeout while calling CacheFlush handler

The CacheFlush implementation does not respect RandomTimeout value.
All cache values, whose flush is deferred by RandomTimeout variance,
will be flushed. That can cause a partial or full cache flush,
depending on the value of RandomTimeout.

diff --git a/src/collectd.conf.pod b/src/collectd.conf.pod
index 27acc99..f94669a 100644 (file)
--- a/src/collectd.conf.pod
+++ b/src/collectd.conf.pod
@@ -6469,12 +6469,12 @@ it writes all values for a certain RRD-file if the oldest value is older than
 (or equal to) the number of seconds specified by B<CacheTimeout>.
 That check happens on new values arriwal. If some RRD-file is not updated
 anymore for some reason (the computer was shut down, the network is broken,
-etc.) some values may still be in the cache. If B<CacheFlush> is set, then the
-entire cache is searched for entries older than B<CacheTimeout> seconds and
-written to disk every I<Seconds> seconds. Since this is kind of expensive and
-does nothing under normal circumstances, this value should not be too small.
-900 seconds might be a good value, though setting this to 7200 seconds doesn't
-normally do much harm either.
+etc.) some values may still be in the cache. If B<CacheFlush> is set, then
+every I<Seconds> seconds the entire cache is searched for entries older than
+B<CacheTimeout> + B<RandomTimeout> seconds. The entries found are written to
+disk. Since entire cache scan is kind of expensive and does nothing under normal
+circumstances, this value should not be too small. 900 seconds might be a good
+value, though setting this to 7200 seconds doesn't normally do much harm either.
 
 Default value for this option is 10x of B<CacheTimeout>.
 If value of B<CacheFlush> less than value of B<CacheTimeout> then default value

diff --git a/src/rrdtool.c b/src/rrdtool.c
index 0f02ffc..dd2df0f 100644 (file)
--- a/src/rrdtool.c
+++ b/src/rrdtool.c
@@ -726,7 +726,7 @@ static int rrd_cache_insert(const char *filename, const char *value,
 
   if ((cache_timeout > 0) &&
       ((cdtime() - cache_flush_last) > cache_flush_timeout))
-    rrd_cache_flush(cache_timeout);
+    rrd_cache_flush(cache_timeout + random_timeout);
 
   pthread_mutex_unlock(&cache_lock);